In the past, to obtain ion conduction between electrodes in secondary cells, fuel cells, dye sensitized solar cells, actuators, and other electrochemical devices, a liquid electrolyte comprised of an electrolytic salt dissolved in a solvent has been used. However, with a liquid electrolyte using a solvent, reduction in the amount of liquid along with time due to evaporation of the solvent or liquid leakage is liable to occur, so development of an alternative electrolyte has been studied.
As an alternative electrolyte to a liquid electrolyte using a solvent, utilization of a nonvolatile ionic liquid has been studied. For example, Patent Document 1 proposes an electrolyte composition which contains an imidazolium compound or a pyridinium compound which has an oligoether group as a substituent. By using such an ionic liquid as an electrolyte, the problem of the reduction in the amount of liquid along with time due to evaporation of the solvent or liquid leakage which is seen in a liquid electrolyte using a solvent can be improved. However, a liquid is still used as the electrolyte, so there are the problems that handling is not easy at the time of production of an electrochemical device and, further, the problem of liquid leakage at the time of use is not completely solved.
Therefore, use of a polymer material which is excellent in ion conductivity as an electrolyte (a so-called “polymer electrolyte”) has been studied. For example, Patent Document 2 proposes use, as an electrolyte composition, of a polyether compound which is comprised of a polyalkylene oxide main chain, ionic side chains, and counter ions of ionic side chains wherein the ionic side chains or counter ions exhibit liquid crystallinity. Further, Patent Document 3 proposes a solid electrolyte composition using a polymer compound which has cationic structures at the main chain or side chains and which has halide ions or polyhalide ions as counter anions of the cationic structures. These electrolyte compositions are solid in form exhibiting almost no fluidity in the normal usage environment of the electrolyte, so the problem of liquid leakage at the time of use of the electrochemical device is solved.
However, the electrolyte composition which is described in Patent Document 2 and Patent Document 3 is solid in form, so is inferior in degree of freedom when applied as an electrolyte for an electrochemical device. For example, there was the problem that it was not easy to coat it or impregnate it at other members. For this reason, a material which is excellent in workability to an extent enabling other members to be coated or impregnated and which can give an electrolyte which is prevented from liquid leakage and is excellent in shape retention after being worked has been fervently desired.